{"id":1118,"date":"2017-10-19T13:49:35","date_gmt":"2017-10-19T13:49:35","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/?post_type=chapter&#038;p=1118"},"modified":"2018-10-05T17:23:32","modified_gmt":"2018-10-05T17:23:32","slug":"oxidation-of-alkenes-epoxidation","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/chapter\/oxidation-of-alkenes-epoxidation\/","title":{"raw":"Oxidation of Alkenes: Epoxidation","rendered":"Oxidation of Alkenes: Epoxidation"},"content":{"raw":"<div class=\"elm-header\">\r\n<div class=\"textbox learning-objectives\">\r\n<h3>Objectives<\/h3>\r\n<div id=\"elm-main-content\" class=\"elm-content-container\">\r\n<div>\r\n<div id=\"skills\">\r\n\r\nAfter completing this section, you should be able to\r\n<ol>\r\n \t<li>write the equation for the epoxidation of an alkene using meta-chloroperoxybenzoic acid.<\/li>\r\n \t<li>identify the alkene, reagents, or both, that must be used to prepare a given epoxide.<\/li>\r\n \t<li>write the equation for the hydroxylation of an alkene using osmium tetroxide, and draw the structure of the cyclic intermediate.<\/li>\r\n \t<li>draw the structure of the diol formed from the reaction of a given alkene with osmium tetroxide.<\/li>\r\n \t<li>identify the alkene, the reagents, or both, that must be used to prepare a given 1,2-diol.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div id=\"elm-main-content\" class=\"elm-content-container\">\r\n<div>\r\n<div class=\"textbox key-takeaways\">\r\n<h3>Key Terms<\/h3>\r\nMake certain that you can define, and use in context, the key terms below.\r\n<ul>\r\n \t<li>diol<\/li>\r\n \t<li>glycol<\/li>\r\n \t<li>hydroxylation<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\nOxacyclopropane rings, also called <span class=\"external\">epoxide<\/span> rings, are useful reagents that may be opened by further reaction to form anti vicinal diols. One way to synthesize oxacyclopropane rings is through the reaction of an alkene with <span class=\"external\">peroxycarboxylic acid<\/span>.\r\n<div id=\"section_1\">\r\n<h3 class=\"editable\">Oxacyclopropane Synthesis by Peroxycarboxylic Acid<\/h3>\r\nOxacyclopropane synthesis by peroxycarboxylic acid requires an alkene and a peroxycarboxylic acid as well as an appropriate solvent. The peroxycarboxylic acid has the unique property of having an electropositive oxygen atom on the COOH group. The reaction is initiated by the electrophilic oxygen atom reacting with the nucleophilic carbon-carbon double bond. The mechanism involves a concerted reaction with a four-part, circular transition state. The result is that the originally electropositive oxygen atom ends up in the oxacyclopropane ring and the COOH group becomes COH.\r\n\r\n<\/div>\r\n<div id=\"section_2\">\r\n<h3 class=\"editable\">Mechanism<\/h3>\r\nPeroxycarboxylic acids are generally unstable. An exception is <span class=\"external\">meta-chloroperoxybenzoic acid<\/span>, shown in the mechanism above. Often abbreviated MCPBA, it is a stable crystalline solid. Consequently, MCPBA is popular for laboratory use. However, MCPBA can be explosive under some conditions.\r\n\r\n<img class=\"internal aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142511\/transition_state_b_2.png\" alt=\"\" width=\"557\" height=\"156\" \/>\r\n\r\nPeroxycarboxylic acids are sometimes replaced in industrial applications by monoperphthalic acid, or the monoperoxyphthalate ion bound to magnesium, which gives magnesium monoperoxyphthalate (MMPP). In either case, a nonaqueous solvent such as <span class=\"external\">chloroform<\/span>, <span class=\"external\">ether<\/span>, <span class=\"external\">acetone<\/span>, or <span class=\"external\">dioxane<\/span> is used. This is because in an aqueous medium with any acid or base catalyst present, the epoxide ring is hydrolyzed to form a vicinal <span class=\"external\">diol<\/span>, a molecule with two OH groups on neighboring carbons. (For more explanation of how this reaction leads to vicinal diols, see below.) However, in a nonaqueous solvent, the hydrolysis is prevented and the epoxide ring can be isolated as the product. Reaction yields from this reaction are usually about 75%. The reaction rate is affected by the nature of the alkene, with more nucleophilic double bonds resulting in faster reactions.\r\n<div>\r\n<div id=\"example\">\r\n<div class=\"textbox examples\">\r\n<h3>Example<\/h3>\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142513\/example_rxn_1.png\" alt=\"example_rxn (1).png\" width=\"536\" height=\"150\" \/>\r\n\r\nSince the transfer of oxygen is to the same side of the double bond, the resulting oxacyclopropane ring will have the same stereochemistry as the starting alkene. A good way to think of this is that the alkene is rotated so that some constituents are coming forward and some are behind. Then, the oxygen is inserted on top. (See the product of the above reaction.) One way the <span class=\"external\">epoxide<\/span> ring can be opened is by an acid catalyzed oxidation-hydrolysis. Oxidation-hydrolysis gives a vicinal <span class=\"external\">diol<\/span>, a molecule with OH groups on neighboring carbons. For this reaction, the dihydroxylation is <em>anti<\/em> since, due to steric hindrance, the ring is attacked from the side opposite the existing oxygen atom. Thus, if the starting alkene is trans, the resulting vicinal diol will have one S and one R <span class=\"external\">stereocenter<\/span>. But, if the starting alkene is cis, the resulting vicinal diol will have a racemic mixture of S, S and R, R <span class=\"external\">enantiomers<\/span>.\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div id=\"section_3\">\r\n<div class=\"textbox examples\">\r\n<h3>Examples<\/h3>\r\n<div id=\"section_3\">\r\n<h3 class=\"editable\">Problems<\/h3>\r\n1. Predict the product of the reaction of cis-2-hexene with MCPBA (meta-chloroperoxybenzoic acid)\r\n\r\na) in acetone solvent.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142515\/1_a.png\" alt=\"1_a.png\" width=\"304px\" height=\"84px\" \/>\r\n\r\nb) in an aqueous medium with acid or base catalyst present.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142517\/1_b.png\" alt=\"1_b.png\" width=\"409px\" height=\"94px\" \/>\r\n\r\n2. Predict the product of the reaction of trans-2-pentene with magnesium monoperoxyphthalate (MMPP) in a chloroform solvent.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142518\/2.png\" alt=\"2.png\" width=\"410px\" height=\"84px\" \/>\r\n\r\n3. Predict the product of the reaction of trans-3-hexene with MCPBA in ether solvent.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142520\/3.png\" alt=\"3.png\" width=\"411px\" height=\"85px\" \/>\r\n\r\n4. Predict the reaction of propene with MCPBA.\r\n\r\na) in acetone solvent\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142522\/4a.png\" alt=\"4a.png\" width=\"402px\" height=\"77px\" \/>\r\n\r\nb) after aqueous work-up.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142524\/4b.png\" alt=\"4b.png\" width=\"405px\" height=\"87px\" \/>\r\n\r\n5. Predict the reaction of cis-2-butene in chloroform solvent.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142526\/5_1.png\" alt=\"5 (1).png\" width=\"245px\" height=\"66px\" \/>\r\n\r\n<\/div>\r\n<div id=\"section_4\">\r\n<h3 class=\"editable\">Answers<\/h3>\r\n1. \u00a0\u00a0\u00a0\u00a0a) [reveal-answer q=\"591890\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"591890\"]Cis-2-methyl-3-propyloxacyclopropane\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142528\/1_a_ans.png\" alt=\"1_a_ans.png\" width=\"535px\" height=\"156px\" \/>[\/hidden-answer]\r\n\r\nb) [reveal-answer q=\"822359\"]Show Answer[\/reveal-answer]\r\n\r\n[hidden-answer a=\"822359\"]Racemic (2R,3R)-2,3-hexanediol and (2S,3S)-2,3-hexanediol[\/hidden-answer]\r\n\r\n<a title=\"1_b_ans.png\" href=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2064\/1_b_ans.png?revision=1\" rel=\"internal\"><img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142529\/1_b_ans.png\" alt=\"1_b_ans.png\" width=\"720px\" height=\"133px\" \/><\/a>\r\n\r\n2.\u00a0 \u00a0[reveal-answer q=\"411940\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"411940\"]Trans-3-ethyl-2-methyloxacyclopropane.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142531\/2_ans.png\" alt=\"2_ans.png\" width=\"567px\" height=\"135px\" \/>[\/hidden-answer]\r\n\r\n3.\u00a0 \u00a0 [reveal-answer q=\"372846\"]Show Answer[\/reveal-answer]\r\n\r\n[hidden-answer a=\"372846\"] Trans-3,4-diethyloxacyclopropane.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142533\/3_ans.png\" alt=\"3_ans.png\" width=\"695px\" height=\"116px\" \/>[\/hidden-answer]\r\n\r\n4. [reveal-answer q=\"481039\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"481039\"]\r\n\r\na) 1-ethyl-oxacyclopropane\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142535\/4a_ans.png\" alt=\"4a_ans.png\" width=\"435px\" height=\"94px\" \/>[\/hidden-answer]\r\n\r\nb) [reveal-answer q=\"249193\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"249193\"]Racemic (2S)-1,2-propandiol and (2R)-1,2-propanediol\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142536\/4b_ans.png\" alt=\"4b_ans.png\" width=\"678px\" height=\"145px\" \/>[\/hidden-answer]\r\n\r\n5.[reveal-answer q=\"559966\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"559966\"] Cis-2,3-dimethyloxacyclopropane\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142538\/5_ans_4.png\" alt=\"5_ans_4.png\" width=\"478px\" height=\"152px\" \/>[\/hidden-answer]\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div id=\"section_5\">\r\n<h3 class=\"editable\">Anti Dihydroxylation<\/h3>\r\nEpoxides may be cleaved by aqueous acid to give glycols that are often diastereomeric with those prepared by the <a class=\"external\" title=\"http:\/\/www2.chemistry.msu.edu\/faculty\/reusch\/VirtTxtJml\/addene2.htm#add4b\" href=\"http:\/\/www2.chemistry.msu.edu\/faculty\/reusch\/VirtTxtJml\/addene2.htm#add4b\" target=\"_blank\" rel=\"external nofollow noopener\">syn-hydroxylation reaction<\/a> described above. Proton transfer from the acid catalyst generates the conjugate acid of the epoxide, which is attacked by nucleophiles such as water in the same way that the cyclic bromonium ion described above undergoes reaction. The result is <strong>anti-hydroxylation<\/strong> of the double bond, in contrast to the syn-stereoselectivity of the earlier method. In the following equation this procedure is illustrated for a cis-disubstituted epoxide, which, of course, could be prepared from the corresponding cis-alkene. This hydration of an epoxide does not change the oxidation state of any atoms or groups.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142542\/epoxhydr.gif\" alt=\"epoxhydr.gif\" width=\"720px\" height=\"110px\" \/>\r\n\r\n<\/div>\r\n<div id=\"section_6\">\r\n<h3 class=\"editable\">Syn Dihydroxylation<\/h3>\r\nOsmium tetroxide oxidizes alkenes to give glycols through syn addition. A glycol, also known as a vicinal diol, is a compound with two -OH groups on adjacent carbons.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2134\/glycol.bmp?revision=1&amp;size=bestfit&amp;width=99&amp;height=64#fixme\" alt=\"glycol.bmp\" width=\"99px\" height=\"64px\" \/>\r\n\r\n<\/div>\r\n<div id=\"section_7\">\r\n<h3 class=\"editable\">Introduction<\/h3>\r\nThe reaction with $$OsO_4$$ is a concerted process that has a cyclic intermediate and no rearrangements. Vicinal syn dihydroxylation complements the epoxide-hydrolysis sequence which constitutes an <em>anti <\/em>dihydroxylation of an alkene. When an alkene reacts with osmium tetroxide, stereocenters can form in the glycol product. Cis alkenes give <a class=\"internal\" title=\"Wikitexts\/UCD Chem 118A\/ChemWiki Module Topics for Chem 118B\/Meso Compounds\" href=\"https:\/\/chem.libretexts.org\/Core\/Organic_Chemistry\/Chirality\/Meso_Compounds\" rel=\"internal\">meso<\/a>\u00a0products and trans alkenes give <a title=\"Racemic Mixtures\" href=\"https:\/\/chem.libretexts.org\/Core\/Organic_Chemistry\/Fundamentals\/Isomerism_in_Organic_Compounds\/Racemic_Mixtures\" rel=\"internal\">racemic\u00a0mixtures<\/a>.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2129\/Cis_alkenes.bmp?revision=1&amp;size=bestfit&amp;width=438&amp;height=282#fixme\" alt=\"Cis alkenes.bmp\" width=\"438px\" height=\"282px\" \/>\r\n\r\n$$OsO_4$$ is formed slowly when osmium powder reacts with gasoues $$O_2$$ at ambient temperature. Reaction of bulk solid requires heating to 400 \u00b0C:\r\n\r\n\\[Os_{(s)} +\u00a02O_{2\\;(g)} \\rightarrow OS_4\\]\r\n\r\nSince Osmium tetroxide is expensive and highly toxic, the reaction with alkenes has been modified. Catalytic amounts of OsO<sub>4<\/sub> and stoichiometric amounts of an oxidizing agent such as hydrogen peroxide are now used to eliminate some hazards. Also, an older reagent that was used instead of OsO<sub>4<\/sub> was potassium permanganate, $$KMnO_4$$. Although syn diols will result from the reaction of KMnO<sub>4<\/sub> and an alkene, potassium permanganate is less useful since it gives poor yields of the product because of <em>overoxidation<\/em>.\r\n\r\n<\/div>\r\n<div id=\"section_8\">\r\n<h3 class=\"editable\"><strong>Mechanism<\/strong><\/h3>\r\n<ul>\r\n \t<li>Electrophilic attack on the alkene\r\n<ul>\r\n \t<li>Pi bond of the alkene acts as the nucleophile and reacts with osmium (VIII) tetroxide (OsO<sub>4<\/sub>)<\/li>\r\n \t<li>2 electrons from the double bond flows toward the osmium metal\r\n<ul>\r\n \t<li>In the process, 3 electron pairs move simultaneously<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li>Cyclic ester with Os\u00a0(VI)\u00a0is produced<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li>Reduction\r\n<ul>\r\n \t<li>H<sub>2<\/sub>S reduces the cyclic ester\r\n<ul>\r\n \t<li>NaHSO<sub>4<\/sub> with H<sub>2<\/sub>O\u00a0may be used<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li>Forms the syn-1,2-diol (glycol)<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\nExample:\u00a0Dihydroxylation of 1-ethyl-1-cycloheptene\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2133\/example.bmp?revision=1&amp;size=bestfit&amp;width=715&amp;height=197#fixme\" alt=\"example.bmp\" width=\"715px\" height=\"197px\" \/>\r\n\r\n<\/div>\r\n<div id=\"section_9\">\r\n<h3 class=\"editable\">Hydroxylation of alkenes<\/h3>\r\nDihydroxylated products (glycols) are obtained by reaction with aqueous potassium permanganate (pH &gt; 8) or osmium tetroxide in pyridine solution. Both reactions appear to proceed by the same mechanism (shown below); the metallocyclic intermediate may be isolated in the osmium reaction. In basic solution the purple permanganate anion is reduced to the green manganate ion, providing a nice color test for the double bond functional group. From the mechanism shown here we would expect syn-stereoselectivity in the bonding to oxygen, and regioselectivity is not an issue.\r\n\r\n<img class=\"aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142544\/glycolfm.gif\" alt=\"image\" \/>\r\n\r\nWhen viewed in context with the previously discussed addition reactions, the hydroxylation reaction might seem implausible. Permanganate and osmium tetroxide have similar configurations, in which the metal atom occupies the center of a tetrahedral grouping of negatively charged oxygen atoms. How, then, would such a species interact with the nucleophilic pi-electrons of a double bond? A possible explanation is that an empty d-orbital of the electrophilic metal atom extends well beyond the surrounding oxygen atoms and initiates electron transfer from the double bond to the metal, in much the same fashion noted above for platinum. Back-bonding of the nucleophilic oxygens to the antibonding \u03c0*-orbital completes this interaction. The result is formation of a metallocyclic intermediate, as shown above.\r\n\r\n<\/div>\r\n<div id=\"section_10\">\r\n<h3 class=\"editable\"><strong>Chemical Highlight<\/strong><\/h3>\r\nAntitumor drugs have been formed by using dihydroxylation. This method has been applied to the enantioselective synthesis of ovalicin, which is a class of fungal-derived products called antiangiogenesis agents. These antitumor products can cut off the blood supply to solid tumors. A derivative of ovalicin, TNP-470, is chemically stable, nontoxic, and noninflammatory. TNP-470 has been used in research to determine its effectiveness in treating cancer of the breast, brain, cervix, liver, and prostate.\r\n\r\n<\/div>\r\n<div id=\"section_11\">\r\n<h3 class=\"editable\">Outside links<\/h3>\r\n<ul>\r\n \t<li><a class=\"external\" href=\"http:\/\/en.wikipedia.org\/wiki\/Osmium_tetroxide\" target=\"_blank\" rel=\"external nofollow noopener\">http:\/\/en.wikipedia.org\/wiki\/Osmium_tetroxide<\/a><\/li>\r\n \t<li><a class=\"external\" href=\"http:\/\/www.chm.bris.ac.uk\/motm\/oso4\/oso4v.htm\" target=\"_blank\" rel=\"external nofollow noopener\">http:\/\/www.chm.bris.ac.uk\/motm\/oso4\/oso4v.htm<\/a><\/li>\r\n \t<li><a class=\"external\" href=\"http:\/\/www.organic-chemistry.org\/chemicals\/oxidations\/osmiumtetroxide.shtm\" target=\"_blank\" rel=\"external nofollow noopener\">http:\/\/www.organic-chemistry.org\/chemicals\/oxidations\/osmiumtetroxide.shtm<\/a><\/li>\r\n<\/ul>\r\n<\/div>\r\n<div id=\"section_12\">\r\n<h3 class=\"editable\">References<\/h3>\r\n<ol>\r\n \t<li>Dehestani, Ahmad et al. (2005). Ligand-assisted reduction of osmium tetroxide with molecular hydrogen via a [3+2] mechanism. <em>Journal of the American Chemical Society, 2005, 127 (10), <\/em>3423-3432.<\/li>\r\n \t<li>Sorrell, Thomas, N. <u>Organic Chemistry<\/u>. New York:\u00a0University Science Books, 2006.<\/li>\r\n \t<li>Vollhardt, Peter, and Neil E. Schore. <u>Organic\u00a0Chemistry:\u00a0Structure and Function<\/u>.\u00a05th Edition.\u00a0New York:\u00a0W.\u00a0H. Freeman &amp;\u00a0Company, 2007.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<div id=\"section_13\">\r\n<div class=\"textbox examples\">\r\n<h3>Examples<\/h3>\r\n<div id=\"section_13\">\r\n<h3 class=\"editable\">Problems<\/h3>\r\nQuestions:\r\n\r\n1. Give the major product.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2136\/Problem_1_(1).bmp?revision=1&amp;size=bestfit&amp;width=131&amp;height=51#fixme\" alt=\"Problem 1 (1).bmp\" width=\"131px\" height=\"51px\" \/>\r\n\r\n2. What is the product in the dihydroxylation of (Z)-3-hexene?\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2139\/Problem_2.bmp?revision=1&amp;size=bestfit&amp;width=248&amp;height=59#fixme\" alt=\"Problem 2.bmp\" width=\"248px\" height=\"59px\" \/>\r\n\r\n3. What is the product in the dihydroxylation of (E)-3-hexene?\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2141\/Problem_3.bmp?revision=1&amp;size=bestfit&amp;width=464&amp;height=98#fixme\" alt=\"Problem 3.bmp\" width=\"464px\" height=\"98px\" \/>\r\n\r\n4. Draw the intermediate of this reaction.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2142\/Problem_4.bmp?revision=1&amp;size=bestfit&amp;width=253&amp;height=125#fixme\" alt=\"Problem 4.bmp\" width=\"253px\" height=\"125px\" \/>\r\n\r\n5. Fill in the missing reactants, reagents, and product.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2144\/Problem_5.bmp?revision=1&amp;size=bestfit&amp;width=528&amp;height=90#fixme\" alt=\"Problem 5.bmp\" width=\"528px\" height=\"90px\" \/>\r\n\r\n<\/div>\r\n<div id=\"section_14\">\r\n<h3 class=\"editable\">Solutions<\/h3>\r\n1. [reveal-answer q=\"13939\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"13939\"]A syn-1,2-ethanediol is formed. There is no stereocenter in this particular reaction.\r\n\r\nThe OH groups are on the same side.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2120\/Answer_1.bmp?revision=1&amp;size=bestfit&amp;width=96&amp;height=63#fixme\" alt=\"Answer 1.bmp\" width=\"96px\" height=\"63px\" \/>[\/hidden-answer]\r\n\r\n2.\r\n[reveal-answer q=\"412717\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"412717\"]Meso-3,4-hexanediol is formed. There are 2 stereocenters in this reaction.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2122\/Answer_2.bmp?revision=1&amp;size=bestfit&amp;width=131&amp;height=108#fixme\" alt=\"Answer 2.bmp\" width=\"131px\" height=\"108px\" \/>[\/hidden-answer]\r\n\r\n3. [reveal-answer q=\"632316\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"632316\"]A racemic mixture of 3,4-hexanediol is formed. There are 2 stereocenters in both products.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2124\/Answer_3.bmp?revision=1&amp;size=bestfit&amp;width=720&amp;height=112#fixme\" alt=\"Answer 3.bmp\" width=\"720px\" height=\"112px\" \/>[\/hidden-answer]\r\n\r\n4. [reveal-answer q=\"780244\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"780244\"]A cyclic osmic ester is formed.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2125\/Answer_4.bmp?revision=1&amp;size=bestfit&amp;width=163&amp;height=155#fixme\" alt=\"Answer 4.bmp\" width=\"163px\" height=\"155px\" \/>[\/hidden-answer]\r\n\r\n5.[reveal-answer q=\"648565\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"648565\"] The Diels-Alder cycloaddition reaction\u00a0is needed in the first box to form the cyclohexene. The second box needs a reagent to reduce the intermediate cyclic ester (not shown). The third box has the product: 1,2-cyclohexanediol.\r\n\r\n<img class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2127\/Answer_5.bmp?revision=1&amp;size=bestfit&amp;width=481&amp;height=90#fixme\" alt=\"Answer 5.bmp\" width=\"481px\" height=\"90px\" \/>[\/hidden-answer]\r\n\r\n<\/div>\r\n<div id=\"section_15\"><\/div>\r\n<\/div>\r\n<\/div>\r\n<div id=\"section_15\">\r\n<h3 class=\"editable\">Contributors<\/h3>\r\n<ul>\r\n \t<li><a class=\"external\" title=\"http:\/\/science.athabascau.ca\/staff-pages\/dietmark\" href=\"http:\/\/science.athabascau.ca\/staff-pages\/dietmark\" target=\"_blank\" rel=\"external nofollow noopener\">Dr. Dietmar Kennepohl<\/a> FCIC (Professor of Chemistry, <a class=\"external\" title=\"http:\/\/www.athabascau.ca\/\" href=\"http:\/\/www.athabascau.ca\/\" target=\"_blank\" rel=\"external nofollow noopener\">Athabasca University<\/a>)<\/li>\r\n \t<li>Prof. Steven Farmer (<a class=\"external\" title=\"http:\/\/www.sonoma.edu\" href=\"http:\/\/www.sonoma.edu\" target=\"_blank\" rel=\"external nofollow noopener\">Sonoma State University<\/a>)<\/li>\r\n \t<li>Shivam Nand<\/li>\r\n \t<li><a title=\"Organic_Chemistry_With_a_Biological_Emphasis\" href=\"https:\/\/chem.libretexts.org\/Textbook_Maps\/Organic_Chemistry_Textbook_Maps\/Map%3A_Organic_Chemistry_with_a_Biological_Emphasis_(Soderberg)\" rel=\"internal\">Organic Chemistry With a Biological Emphasis <\/a>by\u00a0<a class=\"external\" title=\"http:\/\/facultypages.morris.umn.edu\/~soderbt\/\" href=\"http:\/\/facultypages.morris.umn.edu\/%7Esoderbt\/\" target=\"_blank\" rel=\"external nofollow noopener\">Tim Soderberg<\/a>\u00a0(University of Minnesota, Morris)<\/li>\r\n \t<li>Kristen Perano<\/li>\r\n \t<li><\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>","rendered":"<div class=\"elm-header\">\n<div class=\"textbox learning-objectives\">\n<h3>Objectives<\/h3>\n<div id=\"elm-main-content\" class=\"elm-content-container\">\n<div>\n<div id=\"skills\">\n<p>After completing this section, you should be able to<\/p>\n<ol>\n<li>write the equation for the epoxidation of an alkene using meta-chloroperoxybenzoic acid.<\/li>\n<li>identify the alkene, reagents, or both, that must be used to prepare a given epoxide.<\/li>\n<li>write the equation for the hydroxylation of an alkene using osmium tetroxide, and draw the structure of the cyclic intermediate.<\/li>\n<li>draw the structure of the diol formed from the reaction of a given alkene with osmium tetroxide.<\/li>\n<li>identify the alkene, the reagents, or both, that must be used to prepare a given 1,2-diol.<\/li>\n<\/ol>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"elm-main-content\" class=\"elm-content-container\">\n<div>\n<div class=\"textbox key-takeaways\">\n<h3>Key Terms<\/h3>\n<p>Make certain that you can define, and use in context, the key terms below.<\/p>\n<ul>\n<li>diol<\/li>\n<li>glycol<\/li>\n<li>hydroxylation<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<p>Oxacyclopropane rings, also called <span class=\"external\">epoxide<\/span> rings, are useful reagents that may be opened by further reaction to form anti vicinal diols. One way to synthesize oxacyclopropane rings is through the reaction of an alkene with <span class=\"external\">peroxycarboxylic acid<\/span>.<\/p>\n<div id=\"section_1\">\n<h3 class=\"editable\">Oxacyclopropane Synthesis by Peroxycarboxylic Acid<\/h3>\n<p>Oxacyclopropane synthesis by peroxycarboxylic acid requires an alkene and a peroxycarboxylic acid as well as an appropriate solvent. The peroxycarboxylic acid has the unique property of having an electropositive oxygen atom on the COOH group. The reaction is initiated by the electrophilic oxygen atom reacting with the nucleophilic carbon-carbon double bond. The mechanism involves a concerted reaction with a four-part, circular transition state. The result is that the originally electropositive oxygen atom ends up in the oxacyclopropane ring and the COOH group becomes COH.<\/p>\n<\/div>\n<div id=\"section_2\">\n<h3 class=\"editable\">Mechanism<\/h3>\n<p>Peroxycarboxylic acids are generally unstable. An exception is <span class=\"external\">meta-chloroperoxybenzoic acid<\/span>, shown in the mechanism above. Often abbreviated MCPBA, it is a stable crystalline solid. Consequently, MCPBA is popular for laboratory use. However, MCPBA can be explosive under some conditions.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142511\/transition_state_b_2.png\" alt=\"\" width=\"557\" height=\"156\" \/><\/p>\n<p>Peroxycarboxylic acids are sometimes replaced in industrial applications by monoperphthalic acid, or the monoperoxyphthalate ion bound to magnesium, which gives magnesium monoperoxyphthalate (MMPP). In either case, a nonaqueous solvent such as <span class=\"external\">chloroform<\/span>, <span class=\"external\">ether<\/span>, <span class=\"external\">acetone<\/span>, or <span class=\"external\">dioxane<\/span> is used. This is because in an aqueous medium with any acid or base catalyst present, the epoxide ring is hydrolyzed to form a vicinal <span class=\"external\">diol<\/span>, a molecule with two OH groups on neighboring carbons. (For more explanation of how this reaction leads to vicinal diols, see below.) However, in a nonaqueous solvent, the hydrolysis is prevented and the epoxide ring can be isolated as the product. Reaction yields from this reaction are usually about 75%. The reaction rate is affected by the nature of the alkene, with more nucleophilic double bonds resulting in faster reactions.<\/p>\n<div>\n<div id=\"example\">\n<div class=\"textbox examples\">\n<h3>Example<\/h3>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142513\/example_rxn_1.png\" alt=\"example_rxn (1).png\" width=\"536\" height=\"150\" \/><\/p>\n<p>Since the transfer of oxygen is to the same side of the double bond, the resulting oxacyclopropane ring will have the same stereochemistry as the starting alkene. A good way to think of this is that the alkene is rotated so that some constituents are coming forward and some are behind. Then, the oxygen is inserted on top. (See the product of the above reaction.) One way the <span class=\"external\">epoxide<\/span> ring can be opened is by an acid catalyzed oxidation-hydrolysis. Oxidation-hydrolysis gives a vicinal <span class=\"external\">diol<\/span>, a molecule with OH groups on neighboring carbons. For this reaction, the dihydroxylation is <em>anti<\/em> since, due to steric hindrance, the ring is attacked from the side opposite the existing oxygen atom. Thus, if the starting alkene is trans, the resulting vicinal diol will have one S and one R <span class=\"external\">stereocenter<\/span>. But, if the starting alkene is cis, the resulting vicinal diol will have a racemic mixture of S, S and R, R <span class=\"external\">enantiomers<\/span>.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"section_3\">\n<div class=\"textbox examples\">\n<h3>Examples<\/h3>\n<div id=\"section_3\">\n<h3 class=\"editable\">Problems<\/h3>\n<p>1. Predict the product of the reaction of cis-2-hexene with MCPBA (meta-chloroperoxybenzoic acid)<\/p>\n<p>a) in acetone solvent.<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142515\/1_a.png\" alt=\"1_a.png\" width=\"304px\" height=\"84px\" \/><\/p>\n<p>b) in an aqueous medium with acid or base catalyst present.<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142517\/1_b.png\" alt=\"1_b.png\" width=\"409px\" height=\"94px\" \/><\/p>\n<p>2. Predict the product of the reaction of trans-2-pentene with magnesium monoperoxyphthalate (MMPP) in a chloroform solvent.<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142518\/2.png\" alt=\"2.png\" width=\"410px\" height=\"84px\" \/><\/p>\n<p>3. Predict the product of the reaction of trans-3-hexene with MCPBA in ether solvent.<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142520\/3.png\" alt=\"3.png\" width=\"411px\" height=\"85px\" \/><\/p>\n<p>4. Predict the reaction of propene with MCPBA.<\/p>\n<p>a) in acetone solvent<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142522\/4a.png\" alt=\"4a.png\" width=\"402px\" height=\"77px\" \/><\/p>\n<p>b) after aqueous work-up.<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142524\/4b.png\" alt=\"4b.png\" width=\"405px\" height=\"87px\" \/><\/p>\n<p>5. Predict the reaction of cis-2-butene in chloroform solvent.<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142526\/5_1.png\" alt=\"5 (1).png\" width=\"245px\" height=\"66px\" \/><\/p>\n<\/div>\n<div id=\"section_4\">\n<h3 class=\"editable\">Answers<\/h3>\n<p>1. \u00a0\u00a0\u00a0\u00a0a) <\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q591890\">Show Answer<\/span><\/p>\n<div id=\"q591890\" class=\"hidden-answer\" style=\"display: none\">Cis-2-methyl-3-propyloxacyclopropane<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142528\/1_a_ans.png\" alt=\"1_a_ans.png\" width=\"535px\" height=\"156px\" \/><\/div>\n<\/div>\n<p>b) <\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q822359\">Show Answer<\/span><\/p>\n<div id=\"q822359\" class=\"hidden-answer\" style=\"display: none\">Racemic (2R,3R)-2,3-hexanediol and (2S,3S)-2,3-hexanediol<\/div>\n<\/div>\n<p><a title=\"1_b_ans.png\" href=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2064\/1_b_ans.png?revision=1\" rel=\"internal\"><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142529\/1_b_ans.png\" alt=\"1_b_ans.png\" width=\"720px\" height=\"133px\" \/><\/a><\/p>\n<p>2.\u00a0 \u00a0<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q411940\">Show Answer<\/span><\/p>\n<div id=\"q411940\" class=\"hidden-answer\" style=\"display: none\">Trans-3-ethyl-2-methyloxacyclopropane.<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142531\/2_ans.png\" alt=\"2_ans.png\" width=\"567px\" height=\"135px\" \/><\/div>\n<\/div>\n<p>3.\u00a0 \u00a0 <\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q372846\">Show Answer<\/span><\/p>\n<div id=\"q372846\" class=\"hidden-answer\" style=\"display: none\"> Trans-3,4-diethyloxacyclopropane.<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142533\/3_ans.png\" alt=\"3_ans.png\" width=\"695px\" height=\"116px\" \/><\/div>\n<\/div>\n<p>4. <\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q481039\">Show Answer<\/span><\/p>\n<div id=\"q481039\" class=\"hidden-answer\" style=\"display: none\">\n<p>a) 1-ethyl-oxacyclopropane<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142535\/4a_ans.png\" alt=\"4a_ans.png\" width=\"435px\" height=\"94px\" \/><\/div>\n<\/div>\n<p>b) <\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q249193\">Show Answer<\/span><\/p>\n<div id=\"q249193\" class=\"hidden-answer\" style=\"display: none\">Racemic (2S)-1,2-propandiol and (2R)-1,2-propanediol<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142536\/4b_ans.png\" alt=\"4b_ans.png\" width=\"678px\" height=\"145px\" \/><\/div>\n<\/div>\n<p>5.<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q559966\">Show Answer<\/span><\/p>\n<div id=\"q559966\" class=\"hidden-answer\" style=\"display: none\"> Cis-2,3-dimethyloxacyclopropane<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142538\/5_ans_4.png\" alt=\"5_ans_4.png\" width=\"478px\" height=\"152px\" \/><\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"section_5\">\n<h3 class=\"editable\">Anti Dihydroxylation<\/h3>\n<p>Epoxides may be cleaved by aqueous acid to give glycols that are often diastereomeric with those prepared by the <a class=\"external\" title=\"http:\/\/www2.chemistry.msu.edu\/faculty\/reusch\/VirtTxtJml\/addene2.htm#add4b\" href=\"http:\/\/www2.chemistry.msu.edu\/faculty\/reusch\/VirtTxtJml\/addene2.htm#add4b\" target=\"_blank\" rel=\"external nofollow noopener\">syn-hydroxylation reaction<\/a> described above. Proton transfer from the acid catalyst generates the conjugate acid of the epoxide, which is attacked by nucleophiles such as water in the same way that the cyclic bromonium ion described above undergoes reaction. The result is <strong>anti-hydroxylation<\/strong> of the double bond, in contrast to the syn-stereoselectivity of the earlier method. In the following equation this procedure is illustrated for a cis-disubstituted epoxide, which, of course, could be prepared from the corresponding cis-alkene. This hydration of an epoxide does not change the oxidation state of any atoms or groups.<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142542\/epoxhydr.gif\" alt=\"epoxhydr.gif\" width=\"720px\" height=\"110px\" \/><\/p>\n<\/div>\n<div id=\"section_6\">\n<h3 class=\"editable\">Syn Dihydroxylation<\/h3>\n<p>Osmium tetroxide oxidizes alkenes to give glycols through syn addition. A glycol, also known as a vicinal diol, is a compound with two -OH groups on adjacent carbons.<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2134\/glycol.bmp?revision=1&amp;size=bestfit&amp;width=99&amp;height=64#fixme\" alt=\"glycol.bmp\" width=\"99px\" height=\"64px\" \/><\/p>\n<\/div>\n<div id=\"section_7\">\n<h3 class=\"editable\">Introduction<\/h3>\n<p>The reaction with $$OsO_4$$ is a concerted process that has a cyclic intermediate and no rearrangements. Vicinal syn dihydroxylation complements the epoxide-hydrolysis sequence which constitutes an <em>anti <\/em>dihydroxylation of an alkene. When an alkene reacts with osmium tetroxide, stereocenters can form in the glycol product. Cis alkenes give <a class=\"internal\" title=\"Wikitexts\/UCD Chem 118A\/ChemWiki Module Topics for Chem 118B\/Meso Compounds\" href=\"https:\/\/chem.libretexts.org\/Core\/Organic_Chemistry\/Chirality\/Meso_Compounds\" rel=\"internal\">meso<\/a>\u00a0products and trans alkenes give <a title=\"Racemic Mixtures\" href=\"https:\/\/chem.libretexts.org\/Core\/Organic_Chemistry\/Fundamentals\/Isomerism_in_Organic_Compounds\/Racemic_Mixtures\" rel=\"internal\">racemic\u00a0mixtures<\/a>.<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2129\/Cis_alkenes.bmp?revision=1&amp;size=bestfit&amp;width=438&amp;height=282#fixme\" alt=\"Cis alkenes.bmp\" width=\"438px\" height=\"282px\" \/><\/p>\n<p>$$OsO_4$$ is formed slowly when osmium powder reacts with gasoues $$O_2$$ at ambient temperature. Reaction of bulk solid requires heating to 400 \u00b0C:<\/p>\n<p>\\[Os_{(s)} +\u00a02O_{2\\;(g)} \\rightarrow OS_4\\]<\/p>\n<p>Since Osmium tetroxide is expensive and highly toxic, the reaction with alkenes has been modified. Catalytic amounts of OsO<sub>4<\/sub> and stoichiometric amounts of an oxidizing agent such as hydrogen peroxide are now used to eliminate some hazards. Also, an older reagent that was used instead of OsO<sub>4<\/sub> was potassium permanganate, $$KMnO_4$$. Although syn diols will result from the reaction of KMnO<sub>4<\/sub> and an alkene, potassium permanganate is less useful since it gives poor yields of the product because of <em>overoxidation<\/em>.<\/p>\n<\/div>\n<div id=\"section_8\">\n<h3 class=\"editable\"><strong>Mechanism<\/strong><\/h3>\n<ul>\n<li>Electrophilic attack on the alkene\n<ul>\n<li>Pi bond of the alkene acts as the nucleophile and reacts with osmium (VIII) tetroxide (OsO<sub>4<\/sub>)<\/li>\n<li>2 electrons from the double bond flows toward the osmium metal\n<ul>\n<li>In the process, 3 electron pairs move simultaneously<\/li>\n<\/ul>\n<\/li>\n<li>Cyclic ester with Os\u00a0(VI)\u00a0is produced<\/li>\n<\/ul>\n<\/li>\n<li>Reduction\n<ul>\n<li>H<sub>2<\/sub>S reduces the cyclic ester\n<ul>\n<li>NaHSO<sub>4<\/sub> with H<sub>2<\/sub>O\u00a0may be used<\/li>\n<\/ul>\n<\/li>\n<li>Forms the syn-1,2-diol (glycol)<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>Example:\u00a0Dihydroxylation of 1-ethyl-1-cycloheptene<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2133\/example.bmp?revision=1&amp;size=bestfit&amp;width=715&amp;height=197#fixme\" alt=\"example.bmp\" width=\"715px\" height=\"197px\" \/><\/p>\n<\/div>\n<div id=\"section_9\">\n<h3 class=\"editable\">Hydroxylation of alkenes<\/h3>\n<p>Dihydroxylated products (glycols) are obtained by reaction with aqueous potassium permanganate (pH &gt; 8) or osmium tetroxide in pyridine solution. Both reactions appear to proceed by the same mechanism (shown below); the metallocyclic intermediate may be isolated in the osmium reaction. In basic solution the purple permanganate anion is reduced to the green manganate ion, providing a nice color test for the double bond functional group. From the mechanism shown here we would expect syn-stereoselectivity in the bonding to oxygen, and regioselectivity is not an issue.<\/p>\n<p><img decoding=\"async\" class=\"aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1518\/2017\/10\/05142544\/glycolfm.gif\" alt=\"image\" \/><\/p>\n<p>When viewed in context with the previously discussed addition reactions, the hydroxylation reaction might seem implausible. Permanganate and osmium tetroxide have similar configurations, in which the metal atom occupies the center of a tetrahedral grouping of negatively charged oxygen atoms. How, then, would such a species interact with the nucleophilic pi-electrons of a double bond? A possible explanation is that an empty d-orbital of the electrophilic metal atom extends well beyond the surrounding oxygen atoms and initiates electron transfer from the double bond to the metal, in much the same fashion noted above for platinum. Back-bonding of the nucleophilic oxygens to the antibonding \u03c0*-orbital completes this interaction. The result is formation of a metallocyclic intermediate, as shown above.<\/p>\n<\/div>\n<div id=\"section_10\">\n<h3 class=\"editable\"><strong>Chemical Highlight<\/strong><\/h3>\n<p>Antitumor drugs have been formed by using dihydroxylation. This method has been applied to the enantioselective synthesis of ovalicin, which is a class of fungal-derived products called antiangiogenesis agents. These antitumor products can cut off the blood supply to solid tumors. A derivative of ovalicin, TNP-470, is chemically stable, nontoxic, and noninflammatory. TNP-470 has been used in research to determine its effectiveness in treating cancer of the breast, brain, cervix, liver, and prostate.<\/p>\n<\/div>\n<div id=\"section_11\">\n<h3 class=\"editable\">Outside links<\/h3>\n<ul>\n<li><a class=\"external\" href=\"http:\/\/en.wikipedia.org\/wiki\/Osmium_tetroxide\" target=\"_blank\" rel=\"external nofollow noopener\">http:\/\/en.wikipedia.org\/wiki\/Osmium_tetroxide<\/a><\/li>\n<li><a class=\"external\" href=\"http:\/\/www.chm.bris.ac.uk\/motm\/oso4\/oso4v.htm\" target=\"_blank\" rel=\"external nofollow noopener\">http:\/\/www.chm.bris.ac.uk\/motm\/oso4\/oso4v.htm<\/a><\/li>\n<li><a class=\"external\" href=\"http:\/\/www.organic-chemistry.org\/chemicals\/oxidations\/osmiumtetroxide.shtm\" target=\"_blank\" rel=\"external nofollow noopener\">http:\/\/www.organic-chemistry.org\/chemicals\/oxidations\/osmiumtetroxide.shtm<\/a><\/li>\n<\/ul>\n<\/div>\n<div id=\"section_12\">\n<h3 class=\"editable\">References<\/h3>\n<ol>\n<li>Dehestani, Ahmad et al. (2005). Ligand-assisted reduction of osmium tetroxide with molecular hydrogen via a [3+2] mechanism. <em>Journal of the American Chemical Society, 2005, 127 (10), <\/em>3423-3432.<\/li>\n<li>Sorrell, Thomas, N. <u>Organic Chemistry<\/u>. New York:\u00a0University Science Books, 2006.<\/li>\n<li>Vollhardt, Peter, and Neil E. Schore. <u>Organic\u00a0Chemistry:\u00a0Structure and Function<\/u>.\u00a05th Edition.\u00a0New York:\u00a0W.\u00a0H. Freeman &amp;\u00a0Company, 2007.<\/li>\n<\/ol>\n<\/div>\n<div id=\"section_13\">\n<div class=\"textbox examples\">\n<h3>Examples<\/h3>\n<div id=\"section_13\">\n<h3 class=\"editable\">Problems<\/h3>\n<p>Questions:<\/p>\n<p>1. Give the major product.<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2136\/Problem_1_(1).bmp?revision=1&amp;size=bestfit&amp;width=131&amp;height=51#fixme\" alt=\"Problem 1 (1).bmp\" width=\"131px\" height=\"51px\" \/><\/p>\n<p>2. What is the product in the dihydroxylation of (Z)-3-hexene?<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2139\/Problem_2.bmp?revision=1&amp;size=bestfit&amp;width=248&amp;height=59#fixme\" alt=\"Problem 2.bmp\" width=\"248px\" height=\"59px\" \/><\/p>\n<p>3. What is the product in the dihydroxylation of (E)-3-hexene?<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2141\/Problem_3.bmp?revision=1&amp;size=bestfit&amp;width=464&amp;height=98#fixme\" alt=\"Problem 3.bmp\" width=\"464px\" height=\"98px\" \/><\/p>\n<p>4. Draw the intermediate of this reaction.<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2142\/Problem_4.bmp?revision=1&amp;size=bestfit&amp;width=253&amp;height=125#fixme\" alt=\"Problem 4.bmp\" width=\"253px\" height=\"125px\" \/><\/p>\n<p>5. Fill in the missing reactants, reagents, and product.<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2144\/Problem_5.bmp?revision=1&amp;size=bestfit&amp;width=528&amp;height=90#fixme\" alt=\"Problem 5.bmp\" width=\"528px\" height=\"90px\" \/><\/p>\n<\/div>\n<div id=\"section_14\">\n<h3 class=\"editable\">Solutions<\/h3>\n<p>1. <\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q13939\">Show Answer<\/span><\/p>\n<div id=\"q13939\" class=\"hidden-answer\" style=\"display: none\">A syn-1,2-ethanediol is formed. There is no stereocenter in this particular reaction.<\/p>\n<p>The OH groups are on the same side.<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2120\/Answer_1.bmp?revision=1&amp;size=bestfit&amp;width=96&amp;height=63#fixme\" alt=\"Answer 1.bmp\" width=\"96px\" height=\"63px\" \/><\/div>\n<\/div>\n<p>2.<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q412717\">Show Answer<\/span><\/p>\n<div id=\"q412717\" class=\"hidden-answer\" style=\"display: none\">Meso-3,4-hexanediol is formed. There are 2 stereocenters in this reaction.<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2122\/Answer_2.bmp?revision=1&amp;size=bestfit&amp;width=131&amp;height=108#fixme\" alt=\"Answer 2.bmp\" width=\"131px\" height=\"108px\" \/><\/div>\n<\/div>\n<p>3. <\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q632316\">Show Answer<\/span><\/p>\n<div id=\"q632316\" class=\"hidden-answer\" style=\"display: none\">A racemic mixture of 3,4-hexanediol is formed. There are 2 stereocenters in both products.<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2124\/Answer_3.bmp?revision=1&amp;size=bestfit&amp;width=720&amp;height=112#fixme\" alt=\"Answer 3.bmp\" width=\"720px\" height=\"112px\" \/><\/div>\n<\/div>\n<p>4. <\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q780244\">Show Answer<\/span><\/p>\n<div id=\"q780244\" class=\"hidden-answer\" style=\"display: none\">A cyclic osmic ester is formed.<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2125\/Answer_4.bmp?revision=1&amp;size=bestfit&amp;width=163&amp;height=155#fixme\" alt=\"Answer 4.bmp\" width=\"163px\" height=\"155px\" \/><\/div>\n<\/div>\n<p>5.<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q648565\">Show Answer<\/span><\/p>\n<div id=\"q648565\" class=\"hidden-answer\" style=\"display: none\"> The Diels-Alder cycloaddition reaction\u00a0is needed in the first box to form the cyclohexene. The second box needs a reagent to reduce the intermediate cyclic ester (not shown). The third box has the product: 1,2-cyclohexanediol.<\/p>\n<p><img decoding=\"async\" class=\"internal default aligncenter\" src=\"https:\/\/chem.libretexts.org\/@api\/deki\/files\/2127\/Answer_5.bmp?revision=1&amp;size=bestfit&amp;width=481&amp;height=90#fixme\" alt=\"Answer 5.bmp\" width=\"481px\" height=\"90px\" \/><\/div>\n<\/div>\n<\/div>\n<div id=\"section_15\"><\/div>\n<\/div>\n<\/div>\n<div id=\"section_15\">\n<h3 class=\"editable\">Contributors<\/h3>\n<ul>\n<li><a class=\"external\" title=\"http:\/\/science.athabascau.ca\/staff-pages\/dietmark\" href=\"http:\/\/science.athabascau.ca\/staff-pages\/dietmark\" target=\"_blank\" rel=\"external nofollow noopener\">Dr. Dietmar Kennepohl<\/a> FCIC (Professor of Chemistry, <a class=\"external\" title=\"http:\/\/www.athabascau.ca\/\" href=\"http:\/\/www.athabascau.ca\/\" target=\"_blank\" rel=\"external nofollow noopener\">Athabasca University<\/a>)<\/li>\n<li>Prof. Steven Farmer (<a class=\"external\" title=\"http:\/\/www.sonoma.edu\" href=\"http:\/\/www.sonoma.edu\" target=\"_blank\" rel=\"external nofollow noopener\">Sonoma State University<\/a>)<\/li>\n<li>Shivam Nand<\/li>\n<li><a title=\"Organic_Chemistry_With_a_Biological_Emphasis\" href=\"https:\/\/chem.libretexts.org\/Textbook_Maps\/Organic_Chemistry_Textbook_Maps\/Map%3A_Organic_Chemistry_with_a_Biological_Emphasis_(Soderberg)\" rel=\"internal\">Organic Chemistry With a Biological Emphasis <\/a>by\u00a0<a class=\"external\" title=\"http:\/\/facultypages.morris.umn.edu\/~soderbt\/\" href=\"http:\/\/facultypages.morris.umn.edu\/%7Esoderbt\/\" target=\"_blank\" rel=\"external nofollow noopener\">Tim Soderberg<\/a>\u00a0(University of Minnesota, Morris)<\/li>\n<li>Kristen Perano<\/li>\n<li><\/li>\n<\/ul>\n<\/div>\n<\/div>\n","protected":false},"author":44985,"menu_order":6,"template":"","meta":{"_candela_citation":"[]","CANDELA_OUTCOMES_GUID":"","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-1118","chapter","type-chapter","status-publish","hentry"],"part":24,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/pressbooks\/v2\/chapters\/1118","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/wp\/v2\/users\/44985"}],"version-history":[{"count":5,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/pressbooks\/v2\/chapters\/1118\/revisions"}],"predecessor-version":[{"id":2305,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/pressbooks\/v2\/chapters\/1118\/revisions\/2305"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/pressbooks\/v2\/parts\/24"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/pressbooks\/v2\/chapters\/1118\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/wp\/v2\/media?parent=1118"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/pressbooks\/v2\/chapter-type?post=1118"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/wp\/v2\/contributor?post=1118"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/wp-json\/wp\/v2\/license?post=1118"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}